Common coupling for sequential chain firing networks



COMMON COUPLING-FOR SEQUENTIAL CHAIN FIRING NETWORKS Filed June 22, 1949 NN +o ,QI-NIMH me/Mou SAMUEL W. LICHTMAN DANIEL G. MAZUR ATTOR N EY Patented June 13, 1950 UNITED STATES PAT ENT OFFICE COMMUN COUPLING FOR SEQUE'NTIAL CHAIN FIRING NETWORKS Samuel W. Lichtman and'r'Danel G. Mazur, Washington, -'D. C.

Application June 22, 1949, serial No. 100,791

3 Claims.

This invention relates in general to a gas tube timing chain designed for sequential operation such as disclosed in U. S. patent to C. H. Hoep'pner No. 2,457,819, and in particular this invention relates to improvements in the biasing of said series of sequentially operative gas tubes and the coupling of the outputs therefrom.

In the Hoeppner patent there is disclosed a signal generator comprising a cascaded chain of saw-tooth generating primary electron tubes driven from a stable oscillation generator. The primary tubes of the chain are sequentially rendered operative upon vthe joint application thereto of a timing pulse from the oscillation generator and a saw-tooth voltage wave from the preceding primary tube. Coupled to each of the primary tubes is a corresponding secondary tube operative responsive to the output Vof the primary tube to produce a time modulated output pulse. The time occurrence of the time modulated pulse output from each secondary tube is in turn controlled by an intelligence voltage applied thereto.

In the above mentioned system the outputs from the series of secondary tubes, that is the intelligence conveying pulses to be transmitted, were obtained from separate cathode resistors, one for each tube in the chain. With this form of coupling of the outputs, there is encountered a considerable amount of interaction between successively operative stages.

Another disadvantage of the previous circuit resides in the fact that each secondary tube circuit is normally maintained, by cathode biasing, in a non-conductive state. The bias voltage applied to each tube in the chain is extremely critical in that it isessential, in conveying intelligence by time modulated pulses, thatv each secondary tube become operative, in the absence of an intelligence voltage, at the exact same point on the saw-tooth wave. The use of separate cathode resistances and biasing potentials therefore, substantially precludes equalization of cathode bias.

Accordingly it is an object of the present invention to provide a method and means of eliminating interaction between stages of a series of sequentially operative gas filled tubes.

It is a further object of the present invention to provide a simple inexpensive method and means of biasing each sequentially operative gas lled tube circuit.

Another object of the present invention is to provide anovel method and m'eans of coupling the outputs derived irom successively operative gas lled tube circuits.

Further objects and 4attainments will become 2 apparent upon a careful consideration' of the following detailed description when taken in oonjunction with the drawings in which:

Figure 1 is an illustration partly in block and partly schematic of a series of sequentially operative gas lled tubes as taught by the present invention.

vFigure la is 'ain illustration of another embodiment of the present invention and Figure 2 is a series of explanatory waveforms to better illustrate the operation of the series of sequentially operative gas lled tubes.

To more fully understand the purpose and function of the present invention it may best be described in conjunction with the system set forth in the aforementioned U. S. patent to Hoeppner. It is to be expressly understood, however, that the present invention is not to be limited to the generator Vsystem referred to, moreover the present invention may be employed in conjunction with any series of gas filled, or in a' similar manner a series of vacuum' tubes, that are sequentially operative.

With reference to Fig. 1 an intelligence pulse time modulation transmitting system such as disclosed by C. H. Hoeppner is shown partly in block and partly schematic with a series of eX- planatory waveforms shown in Fig. 2. The system is timed in operation by a sinusoidal oscillation signal generator Ill. From the sinusoidal output of generator I0, illustrated at A of Fig. 2, a series of pulse type time reference signals, shown at B in Fig. 2, of short duration are derived by pulse former I'I.

The time reference pulses thus produced, and illustrated at B in Fig. 2, are applied simultaneously via lead l I Ia to a series of gas filled primary electron tubes I2, I3, I4 and I5. Each of such primary tubes corresponds to a different intelligence conveying pulse channel from which successive pulses are transmitted. The number of primary tubes, of course, correspond to the number of intelligence channels desired. The first of the primary tubes I2 may be self-Starting and is made conductive by the injection thereto ofthe first oscillator pulse from pulse former II. The rst primary tube generates upon conduction a saw-tooth Wave form of the type illustrated at C, in Fig. 2. This wave formV is coupled to the second primary tube I3 to render it conductive upon reception of the second oscillator pulse from pulse former I I. This same action continues with the third primarytube in the series and so on until there is vcompleted 'a cycle Vof operation-y through rea'ch'priin'i'y tube'employed'intlie series whereby there is thus generated a sequential series of saw-tooth voltages as illustrated by wave form' C in Fig. 2. The circuit is designed so that no primary tube in the series can be made conductive unless the voltage from the previous primary tube and the oscillator pulse from pulse former I I are simultaneously impressed thereon. This requirement produces sequential operation of the primary tube chain.

With particular reference to the schematic part of Fig. l there is illustrated a practical operative schematic diagram of a series of secondary gaseous pick-oir electron tubes constructed as taught by the present invention. The operation of each pick-E tube is identical, therefore, for purposes of simplicity only the first of the series will be explained in detail. The varying signal from the primary tube I2 is supplied to the grid 29 of a gaseous secondary pickoi electron tube 2. Tube 2 and the similar tubes in the series are normally maintained non-conductive by virtue of cathode biasing voltage supplied in manner to be described later.

The saw-tooth voltage applied to grid 29 from primary tube l2 is in opposition to the average biasing voltage with respect to the cathode. The exact point in the cycle oi' the saw-tooth voltage at which tube i2 becomes conductive is varied by varying the magnitude of the intelligence voltage impressed at terminals 3l. By this means then it is possible to control the time displacement between the initiation of conduction in tube 2 in accordance with a varying voltage signal, such as the intelligence voltage desired to be conveyed applied to terminals 3i.

Termination of conduction in tube 2 is provided by the resistance-capacitance networks 33-341 placed in the anode circuit thereof. Conduction by tube 2 removes more charge from capacitance than can be supplied by resistance 33 permitting the capacitance to discharge, thereby lowering the voltage impressed across the tube. Eventually this voltage falls to a level at which conduction by tube 2 cannot be maintained. Conduction then ceases and the tube becomes inoperative.

As mentioned above, pick-oli 2 and the similar pick-off tube circuits in the series are maintained non-conductive by virtue of a cathode biasing voltage. Since it is essential in conveying intelligence by time modulated pulses that each tube in the series become conductive, in the absence of an intelligence voltage, at the exact same point on its respective saw-tooth Wave, the bias voltage applied to the cathode of each tube in the series is extremely critical. It is normally conventional to supply a separate cathode bias resistor and bias potential for each pick-off tube employed in the series but it has been found to be unnecessary, as well as extremely dinicult in obtaining resistors of exactly equal ohmic value. There is provided in the present invention as illustrated in Fig. .1 a novel means for biasing each pick-off tube in the series. Since each tube fires independently and sequentially, the present invention may employ a common cathode biasing resistor 223 necessitating the choosing of only one resistor and one biasing voltage source 22. In other words a single resistor 2l! and a single voltage source 22 serves as the biasing circuit for all the secondary pick-on? tubes in the circuit, thereby assuring that each tube is so biased to become conductive at the same point. It may be added here that the present invention is not to be limited to cathode biasing, but 1S thusly described merely for illustration. As shown in Fig. la a pair of cathode resistors 20 and 2| tied to point '22 of C-lpotential are employed rather than a single cathode resistor for purposes now to be explained.

It is to be noted upon observance in C of Fig. 2 that the decline of the saw-tooth Wave form is not abrupt but is exponential. This feature of the wave form causes considerable diniculty in that at times the saw-tooth Wave form decay extends into the period of conduction of the next in the series of pick-oir tubes, as shown by the dotted line in C of Fig. 2, causing cross talk and other forms of interaction that interfered with the proper conveyance of intelligence. To eliminate this interaction the present invention is designed so that alternate cathodes are tied to a common output terminal as shown in Fig. 1a, i. e., cathodes I6 and I8 to point 26 and cathodes il and I9 to point 21.

From common points 26 and 2'! the outputs of each pick-off tube are taken at a common terminal 25 through isolating means illustrated in Fig. 1 as crystals 23 and 24 but of course which may be any unilateral impedance elements or any other isolating means known to those skilled in the art. The present invention will further iind application in a system wherein the secondary tube outputs are coupled from the anodes instead of the cathodes.

It is seen then the present invention affords means for supplying to. each cathode in a series of sequentially operative secondary tubes a bias of equal value permitting each tube to become conductive, in the absence of an intelligence voltage, at the exact same point on the saw-tooth wave form and in the presence of an intelligence pulse, in its proper position through the elimination of interaction of the various stages by the common coupling of alternate pick-0E tubes.

Although we have shown only certain and specic embodiments of the present invention, it is to be expressly understood that many modifications are possible thereof without departing from the true spirit of the invention.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. n combination, a series of gas tubes each having a cathode and grid elements therein, means for producing for each of said gas tubes a timing signal of substantially uniformly varying amplitude and for applying said timing Wave to each of said tubes to produce sequential conduction of the tubes, cathode biasing means for normally maintaining said gas tubes in a nonconductive state in the absence of said timing signal comprising connections from each cathode of said series of tubes to a common point, and a resistance connection from said common pointto a source of biasing potential.

2. In combination, a series of gas tubes each having a cathode and grid elements therein, means for producing for each of said gas tubes a timing signal of substantially uniformly varying amplitude and for applying said timing wave to each of said tubes to produce sequential conduction of the tubes, cathode biasing means for normally maintaining said gas tubes in a nonconductive state in the absence of said timing signal comprising connections from the first and alternate cathodes of said series of tubes to a first common point and the remaining cathodes of the series to a second common point, and a resistance connection from both of said common points to a source of biasing potential.

3. In combination, a series of gas tubes each having a cathode and grid elements therein, means for producing for each of said tube components a timing wave c1' substantially uniformly varying amplitude and for applying said Wave to each of said grid elements of said series of tubes to produce conduction therein, means for coupling the outputs of said series of electron tubes comprising direct connections from the rst and alternate cathodes of the series to a rst common point and the remaining cathodes of the 15 2,457,819

series to a second common point, a resistance connection from both of said common points to a source of biasing potential, terminal means, and isolating means connecting both said common points to said terminal means.

SAMUEL W. LICHTMAN. DANIEL G. MAZUR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS- Name Date I-Ioeppner Jan. 4, 1949 Number 

